Numerous methods are known for effecting the conversion of solid carbonaceous materials such as raw particulate coal into useful intermediate products. Generally, these methods comprise the liquefaction of the particulate coal under conditions of elevated temperature and pressures and subsequent separation of the liquefaction product into its constituent solid and liquid fractions. Although the solid fraction has some residual value for use in the production of hydrogen, fuel gas, coker distillates and coke, the liquid fractions recovered as the result of said subsequent separation are the desired and significantly more valued products. The liquid fraction or fractions are more valuable since such fractions represent a source of a variety of liquid hydrocarbons usually obtained only from petroleum and, in addition, can be readily processed by conventional hydrocarbon processing techniques.
Methods also have been devised for accomplishing the simultaneous conversion of mixtures comprised of heavy hydrocarbon materials and solid carbonaceous materials, e.g., oil components and coal. Exemplary of such methods is the process described in U.S. Pat. No. 4,054,504. The process described therein consists of premixing coal and a crude oil comprising at least about 20 percent of residuum oil boiling above about 1,000.degree. F. and subjecting said premix to elevated temperatures and pressures in the presence of hydrogen and a hydrogenation catalyst to convert said coal and the residuum oil components in said crude oil to distillable liquid and gaseous hydrocarbon products. The distillable liquid and gaseous hydrocarbon products are then separated and recovered by conventional means.
A further example of a method for the simultaneous conversion of a blend of a solid carbonaceous material such as coal and a heavy hydrocarbon material such as topped or reduced crude oils is that disclosed in U.S. Pat. No. 4,338,183. Therein is disclosed a method wherein a blend of coal and a topped or reduced crude oil is subjected to elevated temperatures and pressures in a liquefaction zone in the presence of hydrogen and a recycle stream containing substantial quantities of asphaltenes and an unsupported finely divided metal catalyst. A particular objective of the process described in this patent is the extraction of valuable liquid products from the solid carbonaceous material in the blend and the simultaneous conversion of a part of the heavy hydrocarbon material in the blend from a less desirable material to a more desirable material.
Still a further example of a method for the simultaneous conversion of a blend or admixture of a solid carbonaceous material and a heavy hydrocarbon material is co-pending application Ser. No. 653,891 referred to hereinabove. Therein is described a method for the co-processing of an admixture of a solid carbonaceous material, heavy hydrocarbon material, a process-derived recycled solvent system and a disposable metal catalyst. The admixture is subjected to liquefaction, fractionation and subsequent critical solvent extraction with the recovery of various distillable and non-distillable fractions containing mixtures of products derived from the carbonaceous and heavy hydrocarbon materials in the original admixture.
Although the above-referenced methods work quite well for the purposes for which they were developed, there still remains a need for a co-processing method wherein the quantity and quality of distillate products obtainable from such co-processing can be improved.